1. Field of the Invention
The invention is directed to a camming arrangement for a thread handling device.
2. Description of the Prior Art
U.S. Pat. No. 4,263,859 of Ralph E. Johnson for "Thread Handling System for a Sewing Machine", issued Apr. 28, 1981, discloses a thread handling system which includes a thread handling device with elongate members that serve to hold and to meter needle thread to a needle and looptaker of a lockstitch sewing machine. The system further includes a thread tensioner. Thread from a spool extends to the thread tensioner, and beyond the tensioner the thread extends to the thread handling device. Beyond the thread handling device, the thread extends to the needle. A takeup, which brackets the thread handling device, sets stitches and pulls thread through the tensioner. The takeup moves the thread in one direction in the thread handling device to a stitch position at one end of its operating range, and moves in the opposite direction free of thread to the other end of its operating range, after which thread in the device moves to a position of reengagement with the takeup to shorten the path for thread between the tensioner and needle such that a quantity of thread is thereby supplied for use by the needle and looptaker. Copending patent application Ser. No. 357,446 filed Mar. 12, 1982, of Donald Rodda (The Singer Company) for "Thread Handling Arrangement with Fiber Carrying Strip and Cam" discloses such a thread handling system including a thread handling device with a fibrous strip to engage the thread and a thread controlling cam to engage thread exiting from the device. A primary purpose of the cam is to temporarily hold and so delay the descent of thread in the device such that the half-hitching of stitches due to slack thread is prevented. However, despite the improvement achieved with the construction of said application, it has been found that thread will sometimes be drawn off the top end of the cam before needed for stitch formation, and caused to rapidly descend creating slack which on occasion will result in a half-hitched stitch.
It is a principal object of the present invention to provide a thread handling device in a sewing machine with an improved camming arrangement particularly effective to eliminate the formation of defective stitches.
It is another object of the invention to reduce abrasion by and to thread in a thread handling device of the kind disclosed in the aforementioned application.
Other objects and advantages of the invention will become apparent during a reading of the specification when in connection with the accompanying drawings.